MB-100: killed checking_bucket_access

Things appear clearer if we remove one layer of indirection here.

Change-Id: I54e9b44978242a6f637c8db3a04ff9f321250cfd
Reviewed-on: http://review.couchbase.org/27948
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>